Sulfuric acid is conventionally manufactured, transported, and stored in carbon steel vessels. The carbon steel does not corrode in the presence of concentrated sulfuric acid because of the formation of a protective layer of iron sulfate (ferrous sulfate) on the walls and bottom of the vessels. Over time, the iron sulfate layer builds up and in some older vessels can be measured in inches or feet. When vessels are cleaned, the iron sulfate has to be removed. Since it is denser than the acid, it is found in the bottom of the vessel and has to be removed physically, e.g., shoveled out. Alternatively, the iron sulfate may be dissolved with water. However, this method of removal is a problem since dilute sulfuric acid develops with high concentrations of iron sulfate, which is very corrosive.
Development of a suspension system in concentrated sulfuric acid to keep the iron sulfate fluid is a complex problem. Most polymer viscosity enhancers employed in the industry are used in aqueous or organic systems. However, sulfuric acid either reacts with such polymers to form SO.sub.2 and water, or the material is not soluble in it. To date, satisfactory compounds have not been developed for the control of viscosity and suspension of iron sulfate in concentrated sulfuric acid.